1. Field of the Invention
The present invention relates to sensing sound from a particular direction.
2. Background Art
Directional microphone systems are designed to sense sound from a particular set of directions or beam angle while rejecting, filtering out, blocking, or otherwise attenuating sound from other directions. To achieve a high degree of directionality, microphones have been traditionally constructed with one or more sensing elements or transducers held within a mechanical enclosure. The enclosure typically includes one or more acoustic ports for receiving sound and additional material for guiding sound from within the beam angle to sensing elements and blocking sound from other directions.
Directional microphones may be beneficially applied to a variety of applications such as conference rooms, home automation, automotive voice commands, personal computers, telecommunications, personal digital assistants, and the like. These applications typically have one or more desired sources of sound accompanied by one or more noise sources. In some applications with a plurality of desired sources, a desired source may represent a source of noise with regards to another desired source. Also, in many applications microphone characteristics such as size, weight, cost, ability to track a moving source, and the like have a great impact on the success of the application.
Several problems are associated with directional microphones of traditional design. First, to achieve desired directionality, the enclosure is elongated along an axis in the direction of the desired sound. This tends to make directional microphones bulky. Also, microphone transducing elements are often expensive in order to achieve the necessary signal-to-noise ratio and sensitivity required for detecting sounds located some distance from the microphone. Special acoustic materials to direct the desired sound and block unwanted sound add to the microphone cost. Further, highly directional microphones are difficult to aim, requiring large and expensive automated steering systems.
What is needed is directional sound acquisition that permits the microphone to be reduced in both cost and size. Preferably, such directional sound acquisition should be accomplished with existing microphone elements, standard signal processing devices, and the like. Further, a directional sound acquisition system microphone should be steerable towards a sound source.